Patent GB-465726-A (GB)
Title: Improvements in or relating to direct current electric motor control systems
IPC: H02P9/00
Filed: 1935-11-08
Abstract: 465,726. Control of D.C. motors. GENERAL ELECTRIC CO., Ltd., CROFT, E. H., and TURRALL, J. C. Nov. 8, 1935, No. 30950. [Class 38 (iii)] [Also in Group XXXV] Varying E.M.F.-A transmission system in which a D.C. generator having inverse compound characteristics supplies motors which are alternatively in series or parallel and in which the prime mover is governed to run at or near several definite speeds according to the setting of the controller, is provided with generator excitation control means consisting of a variable resistance in a shunt field under the control of a torque motor or watt-meter relay responsive to power developed by the generator. The system is intended to secure the maximum safe loading of the prime mover appropriate to any particular speed while avoiding overloading. Fig. 1 shows the generator and motor circuits and Fig. 2 the control circuits. A generator 1 with shunt winding 2 and decompounding series winding 5 giving a drooping characteristic supplies motors 8, 9, provided with reverse switches 12, 13 and arranged in series or parallel, the generator being driven by a prime mover controlled by relays 35, 36, 37 to run at minimum, intermediate or maximum speeds, for example, 775, 690, and 460 r.p.m., according to the setting of the controller ; the relays 35, 36, 37 are respectively connected to controller contacts 38, 39, 40. Shunt field 2 is supplied from battery 4 through regulating resistance 3, part of which is short-circuited by switches F2, F3 operated by relays F2c, F3c according to the adjustment of the controller, while the remainder of the resistance 3 is cut in or out in steps by switches 47 which are operated by a torque motor or watt-meter relay having current and voltage windings 44, 45, associated with the generator. The torque motor is also influenced by a winding 48 to adapt it to the speed of the prime-mover, winding 48 being in series with the whole or part of resistance 49 when intermediate and maximum speed relays 36, 37 are energized. Starter switch 16 closes circuit through relays M1c, M2c which actuate switches M1, M2 in the battery generator circuit. Switch 25 stops the supply of fuel to the engine when required. In position I of the controller, segment 41 engages contact 38, thus energizing relay 35 giving the minimum speed setting for the engine. Contacts 60, 61 supply motor reversing switches 12, 13 for forward or reverse running according to the adjustment switch 14. Contact 63 closes switch S so that the motors are in series, and also operates switch F1 to connect shunt field 2 with battery 4 through all the resistances 3. Movement to position 11, causes contact 68 to close switch F2 cutting out part of resistance 3. In position III, contact 39 energizes relay 36 to set the engine governor for the intermediate speed, while in position IV contact 70 closes switch F3 and cuts out a further section of resistance 3. In position V, contact 40 adjusts the engine governor for maximum speed running and switch F3 is opened, thus reinserting part of resistance 3 in the field circuit, while movement to position VI cuts out this resistance again. Between positions VI and VII, the motors are changed from series to parallel by operation of switches T1, T2, P, G, S, the order of operation and interconnections being such as to facilitate the transition, and to prevent the paralleling operation from taking place unless some increase in power would result therefrom. In final positions VIII, IX, switches F2, F3 are closed to cut out parts of resistance 3 again. The battery 4 is charged by engine generator 30 and supplies motors 27, 28, 29 driving engine auxiliaries.